To date, cryopreservation is the only method available for medium- and long-term preservation of hematopoietic cell transplants. Indeed, without freezing and at a temperature of 4° C., it was observed that the number and the functional capacity of progenitor cells contained in transplants decreased drastically after only 3 days of preservation (Hechler et al., 1996).
Cryopreservation, however, has notable disadvantages, particularly potential agglutination during thawing or the risk of anaphylactic reaction triggered by the presence of cryoprotectants. Moreover, this method is not applicable to all cell types.
Previous studies have shown that short-term preservation at 4° C. of CD34+ hematopoietic stem cells was improved by modifying the atmospheric conditions of cultures, notably by decreasing the oxygen concentration and increasing the carbon dioxide concentration (Vlaski et al., 2014). Although notable, these improvements remain inadequate to ensure the survival and the maintenance of the functional capacities of cells, and in particular of progenitor cells, for long-term preservation at 4° C.
An optimal method would allow long-term preservation of transplants under hypothermic conditions, without freezing, and would thus simplify transplantation logistics and procedures while improving the results obtained in the recipient.